A 1/2 wavelength plate or 1/4 wavelength plate made of a single sheet of oriented film has heretofore been known. However, such a wavelength plate is disadvantageous in that its retardation differs from wavelength to wavelength, restricting the wavelength at which it can act as a 1/2 wavelength plate or 1/4 wavelength plate to a specific value. In other words, a wavelength plate which acts as a 1/4 wavelength plate with respect to light having a wavelength of 550 nm cannot act as a 1/4 wavelength plate with respect to light having a wavelength of 450 nm or 650 nm. Therefore, when a circular polarizing plate obtained by bonding such a 1/4 wavelength plate to a polarizing plate is used as an anti-reflection filter for preventing reflection from the surface of display or the like, it cannot exert a sufficient anti-reflection effect with respect to light having a wavelength which is not 550 nm, particularly with respect to blue-based light. In this case, the display or the like looks blue.
In this respect, the present inventors earlier proposed a laminated wavelength plate comprising a plurality of oriented films giving a 1/2 wavelength or 114 wavelength laminated with their optical axes crossing each other (JP-A-5-100114 (The term "JP-A" as used herein means an "unexamined published Japanese patent application")). In accordance with this laminated wavelength plate, a predetermined phase difference such as 1/2 wavelength and 1/4 wavelength can be given over a wide wavelength range. However, it was found that such a laminated wavelength plate gives an undesirable retardation in a specific wavelength range. It was also found that a circular polarizing plate made of such a laminated wavelength plate shows too great a reflection at the interface of layers to exhibit sufficient light shielding properties or undergoes a partial retardation change due to heat to give ununiform visual perceptibility.